Republicans and Democrats are urging President Barack Obama to use his final NATO summit to press European leaders to be more aggressive against an old threat from their eastern flank and a new one to their south.

White House officials see the gathering coming at "an inflection point" for NATO and Europe. Beginning Friday in the Polish capital of Warsaw, Western leaders will discuss what seems to be an ever-swelling list of threats that includes a more aggressive Russia, Islamic State attacks and a flood of migrants and refugees from the Middle East and Africa.